Reactive Load and Alternator Speed: Exploring the Relationship

[cnh1995]

A motor driven alternator connected to local load (in lab), say a lamp bank, slows down due to power consumption by the load I.e. nonzero power angle δ. But should it slow down when δ is zero i.e. with purely reactive load(like in SC test and ZPF test)?

 

[Hesch]

should it slow down when δ is zero i.e. with purely reactive load

No it shouldn't, because it cannot deliver energy anywhere ( nobody to consume it ).

A reactive component will consume energy as for one half of a period ( charge a capacitor / induce current in an inductor ), but the energy will be returned it in the next half.

 

[cnh1995]

But if it consumes power in the first half cycle, shouldn't it slow down?

 

[Hesch]

But if it consumes power in the first half cycle, shouldn't it slow down?

Yes, but it will speed up again in the next half cycle. So over time it will not change velocity.

Of course you could say, that the motor will be halted completely within a half periode, because it must charge a capacitor, but then the term "reactive power" does not make sense any longer.